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1.
NIKITIN S.; PR?TZEL-WOLTERS D. 《IMA Journal of Mathematical Control and Information》1991,8(4):431-439
In 1983 Morse proved, for unknown scalar one-dimensional linearsystems, the nonexistence of rational or polynomial universalstabilizers (UAS). In 1983, Nussbaum gave an example of an analyticUAS. In our paper, it is shown that there exist time-invariantpolynomial UAS's with multidimensional gain adaptation. Thedesign procedure is developed for linear, minimum-phase systemsof relative degree one. Convergence of the closed-loop systemis proved. Some numerical simulations are provided. 相似文献
2.
Silver, whose extraordinary electrocatalytical properties for organic halide reduction have been recently evidenced, has been used as cathode material for systematic preparative electrolyses in membrane-divided cells. To better elucidate the substrate role on the remarkable positive shift of reduction potentials, and on the "cage effect" i.e. the promotion of intermolecular reaction on adsorbed intermediates, three halide substrate patterns are here compared in terms of both voltammetric characterization and preparative electroreduction products: aliphatic halides (adamantanes), aromatic halides (phenols) and anomeric glycosyl halides. The preparative electroreductions result mainly in dimerization in the case of glycosyl halides, in H-->Br substitution in the case of bromophenols, in dimerization + substitution in the case of haloadamantanes. The product analysis, both at the end of the reaction and at intermediate times, allows discussing the reaction pathways in terms of intermediate stability and of active surface accessibility. The possibility of complete dehalogenation on a wider substrate variety with remarkably lower energy consumption and almost quantitative current yields makes the process potentially very interesting for environmental purposes. 相似文献
3.
Reference value standards, pH (RVS), for 0.05 mol kg?1 potassium hydrogenphthalate (KHPh) reference buffer solutions in 10, 30, 50 and 70% (w/w) 2-propanol/water solvent mixtures at temperatures from 288.15 to 318.15 K are determined from reversible e.m.f. measurements of the cell Pt¦H2¦KHPh + KCl¦AgCl¦Ag¦Pt. The consistency of the present results is confirmed by multilinear regression analysis of the pH values obtained for each solution composition and temperature, allowing appropriate interpolation of pH (RVS) values within the range of the experiment. The ancillary values of the standard e.m.f. of the cell Pt¦H2¦HCl¦AgCl¦Ag¦Pt are optimized through multilinear regression analysis of the available data in the literature, and the ancillary values of the first ionization constant of o-phthalic acid (H2Ph; benzene-1,2-dicarboxylic acid) in these solvent mixtures are evaluated from reversible e.m.f. measurements of the cell Pt¦H2¦H2Ph + KHPh + KCl¦AgCl¦Ag¦Pt. 相似文献
4.
Torquato Mussini Maurizio Cicognini Paolo Longhi Sandra Rondinini Arthur K. Covington 《Analytica chimica acta》1984
Standard pH(S) values for 0.05 mol kg?1 potassium hydrogenphthalate (KHpH) reference buffer solutions in 10, 30 and 50% (w/w) 1,4-dioxane/water solvent mixtures within the temperature range 288.15–318.15 K are determined from e.m.f. measurements of the cell without transference Pt|H2|KHPh + KCl|AgCl|Ag|Pt. The consistency of the results is analysed by a recently described method of multilinear regression of the quantity p(aHγCl) as a function of both solution composition and temperature. The standard pH(S) determined can be reproduced to within ±0.01 by the equation pH(S) - 4.004 + 3.309w + 0.408z + 1.037w3 - 14.95zw2 + 27.1zw3, where w is the weight fraction of dioxane in the solvent mixture,z = (T –θ)/θ, and θ - 298.15 K. Values of the first ionization constant of phthalic acid (H2Ph; benzene-1,2-dicarboxylic acid) in the above solvent mixtures are also determined from e.m.f. measurements of the cell without transference Pt|H2|H2Ph + KHPh + KCl|AgCl|Ag|Pt. 相似文献
5.
Prof. Tiziana Benincori Dr. Valentina Bonometti Dr. Roberto Cirilli Prof. Patrizia R. Mussini Dr. Andrea Marchesi Prof. Marco Pierini Dr. Tullio Pilati Dr. Simona Rizzo Prof. Francesco Sannicolò 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(1):165-181
A series of tris‐aryl phosphane oxides existing as residual enantiomers or diastereoisomers with substituents on the aryl rings differing in size and electronic properties were synthesized and characterized. Their electronic properties were evaluated on the basis of their electrochemical oxidation and reduction potentials together with those of the corresponding “blade bromides” (i.e., the naphthalene derivatives displaying the same substitution pattern of the tris‐naphthyl phosphane oxide blades, with a bromo substituent where the phosphorus atom is located) determined by CV. The residual stereoisomeric phosphane oxides were isolated in a stereochemically pure state and were found to be highly configurationally stable at room temperature (stereoisomerization barriers of about 27 kcal mol?1). The chiroptical properties of the residual stereoisomers and the assignments of absolute configuration are discussed. The configurational stability of residual tris‐aryl phosphane oxides was found to be scarcely influenced by the electronic properties of the substituents present on the aromatic rings constituting the blades, while steric effects play the most relevant role. Detailed theoretical calculations are in agreement with the experimental results and also contribute to a rational interpretation of the stereodynamics of these systems. 相似文献
6.
Inherently Chiral Macrocyclic Oligothiophenes: Easily Accessible Electrosensitive Cavities with Outstanding Enantioselection Performances
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Prof. Francesco Sannicolò Prof. Patrizia R. Mussini Prof. Tiziana Benincori Dr. Roberto Cirilli Prof. Sergio Abbate Serena Arnaboldi Simone Casolo Dr. Ettore Castiglioni Prof. Giovanna Longhi Dr. Rocco Martinazzo Dr. Monica Panigati Dr. Marco Pappini Dr. Elsa Quartapelle Procopio Dr. Simona Rizzo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(47):15298-15302
Linear conjugated oligothiophenes of variable length and different substitution pattern are ubiquitous in technologically advanced optoelectronic devices, though limitations in application derive from insolubility, scarce processability and chain‐end effects. This study describes an easy access to chiral cyclic oligothiophenes constituted by 12 and 18 fully conjugated thiophene units. Chemical oxidation of an “inherently chiral” sexithiophene monomer, synthesized in two steps from commercially available materials, induces the formation of an elliptical dimer and a triangular trimer endowed with electrosensitive cavities of different tunable sizes. Combination of chirality with electroactivity makes these molecules unique in the current oligothiophenes literature. These macrocycles, which are stable and soluble in most organic solvents, show outstanding chiroptical properties, high circularly polarized luminescence effects and an exceptional enantiorecognition ability. 相似文献
7.
Xiao Chi Ma Bao Jing Zhang Sha Deng Shan Shan Huang Ke Xin Liu Jing Ming Jia 《中国化学快报》2009,20(3):317-319
A new ent-labdane diterpenoid lactone with a new natural product was isolated from Andrographis paniculata. Their structures were elucidated on the basis of spectral evidences including 2D NMR. 相似文献
8.
Dr. Luca Scapinello Sara Grecchi Dr. Sergio Rossi Prof. Fabiana Arduini Dr. Serena Arnaboldi Prof. Andrea Penoni Dr. Roberto Cirilli Prof. Patrizia Romana Mussini Prof. Tiziana Benincori 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(52):13190-13202
A family of inherently chiral electroactive selectors based on the 2,2’-biindole atropisomeric scaffold, of easy synthesis and modulable functional properties, is studied in cascade in two enantioselection contexts. They are at first investigated as probes in enantioselective HPLC, studying molecular structure and temperature effects, and achieving very efficient semipreparative enantioseparation. The enantiomers thus obtained, of remarkable chiroptical features (optical rotation as well as circular dichroism), are successfully applied as selectors in chiral voltammetry in different media for discrimination of the enantiomers of chiral electroactive probes, either by conversion into enantiopure electroactive electrode surfaces by electrooligomerization on glassy carbon substrate (the two monomers with shorter alkyl chains), or as chiral additive in achiral ionic liquid (the monomer with longest alkyl chains). Discrimination is conveniently and reproducibly achieved in terms of significant potential differences for the two enantiomers, specularly inverting either probe or selector configuration. In one case successful discrimination is also observed with the two probe enantiomers concurrently present, either as racemate or with enantiomeric excesses, neatly accounted for by the peak current ratios. 相似文献
9.
Paolo Ferruti Elisabetta Ranucci Amedea Manfredi Nicolò Mauro Elena Ferrari Riccardo Bruni Francesco Colombo Patrizia Mussini Manuela Rossi 《Journal of polymer science. Part A, Polymer chemistry》2012,50(24):5000-5010
Traditional precipitation methods for inorganic micropollutant removal from waters are increasingly being replaced by sorption methods based on both natural and synthetic materials. In this context, two novel effective heavy metal ions absorbers are presented. These resins, LYMA and LMT85, were crosslinked poly(amidoamine)s carrying amine and carboxyl groups in their repeating units. In particular, the LYMA‐repeating unit contains one carboxyl and two amine groups and is a mimic of L ‐lysine, whereas LMT85 contains two amine and five carboxyl groups and is a mimic of EDTA. Both resins were prepared at moderate cost by simple eco‐friendly procedures. The heavy metal ion set adopted as benchmark was Cu2+, Cd2+, Pb2+, Zn2+, Ni2+, and Co2+. LYMA proved selective for Cu2+ and Ni2+, the other ions tested being negligibly absorbed, whereas LMT85 proved capable of rapidly and quantitatively absorbing all the ions tested either singly or in mixed solution. The absorption process was reversible, and the resins were easily regenerated by acidification. The absorption of several metal ions imparted intense coloring to the resins, a feature possibly exploitable for analytical purposes. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
10.
The rationale for the extension of the rH-metric standardization and measurements to aqueous-organic solvent mixtures is here introduced, and examples of establishment of the ranges of conventional rH-metric scales as well as primary standards rHs in some typical aqueous-organic solvent mixtures are described. 相似文献